2011 part B midterm_1

2011 part B midterm_1 - THE UNIVERSITY OF MANITOBA March 3...

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THE UNIVERSITY OF MANITOBA March 3 20 11 MIDTERM EXAMINATION PAPER NO: PAGE NO: 1 of 5 DEPARTMENT & COURSE NO: CHEM 1310 TIME: 2 HOURS EXAMINATION: University I Chemistry: Intro. To Phys. Chem. EXAMINER: CHEM 1310 Committee PART B: Part B will be marked out of a raw score of 20 (or 50% of the 40 marks allotted to this midterm examination). Part B should require approximately 60 min. to complete. DO ALL of QUESTIONS 1 THROUGH 4. NAME: ( Please Print Legibly ) SIGNATURE: STUDENT NUMBER: Examination Room: Seat Number: For Examiner’s use only: 1: 2: 3: ________________ 4: ________________ Total: /20 INSTRUCTIONS: No examination booklets are needed. The questions are to be answered on the pages of this examination as indicated. Write in INK, please. ALL NUMERICAL ANSWERS MUST BE JUSTIFIED WITH PROPER AND CLEAR CALCULATIONS. Blank pages, to the extent that they are not needed for your answers, may also be used for any rough work required to prepare your answer. NOTE THAT YOU MUST ANSWER ALL FOUR QUESTIONS ON THIS PAPER. The allocated marks for each question are shown in brackets to the right of the page after the question. Some information that you may find useful in answering this examination will be found on the DATA PAGES attached to Part A of this examination.
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Paper: CHEM 1310 University I Chemistry: Intro. to Phys. Chem. Page: 2 of 5 (if more space is required to answer these questions, continue on the back side of this page) QUESTION 1 a) A student added 1.250 g of solid ammonium nitrate, NH 4 NO 3 , to 45.0 g of water in a polystyrene coffee cup. The temperature of the water fell from 27.20 to 25.00 °C. Estimate the enthalpy of dissolution of ammonium nitrate, i.e. NH 4 NO 3 (s) NH 4 NO 3 (aq) (Assume that the heat capacity of the coffee cup and thermometer is zero and that the heat capacity of the ammonium nitrate solution is the same as that of water, C sol’n = 4.184 J g -1 K -1 .) (4 marks) Let q diss be the heat needed to dissolve the ammonium nitrate and q soln be the heat lost by the aqueous solution. q diss = # moles of NH 4 NO 3 × Δ diss The molar mass of ammonium nitrate = 2 × 14.0 + 4 × 1.008 + 3 × 16.0 = 80.0 g/mole Therefore # moles of NH 4 NO 3 × = 1.250/80.0 = 0.015625 and q diss = 0.015625 × Δ diss q soln = C p × mass of sol’n ×
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2011 part B midterm_1 - THE UNIVERSITY OF MANITOBA March 3...

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